The specific aim of this training grant renewal proposal is to continue the development of research scientists that are well versed in physics, biology, mathematics, chemistry, engineering and computer science, who also understand the application of these disciplines to the instruments and techniques used in the field of biomedical physics. This field is not limited to the traditional practice of Medical Physics and is much broader in scope. This training program has four basic tracks. The Medical Imaging track investigates the physics of diagnostic radiology modalities (e.g. MRI, MR Spectroscopy, CT) as well as image processing and imaging informatics methods to extract additional information from image data. The Molecular Imaging track investigates the physics of PET, optical and combined imaging modalities, the chemistry and biology of novel imaging tracers and provides investigations of basic biological mechanisms, both normal and pathological. The Radiation Biology track investigates the molecular, cellular, and tissue-related effects of radiation. The importance of factors determining the response of biological systems to clinically relevant radiotherapeutic doses of radiation are covered that deal with classic radiobiology, as well as cutting edge topics of repair, signal transduction, tumor suppressor genes and oncogenes, radiation-induced responses, hypoxia, angiogenesis, carcinogenesis, and gene therapy primarily for small animal imaging. The Therapeutic Medical Physics track investigates novel treatment delivery systems (IMRT - Intensity Modulated Radiation Therapy) and image guidance (IGRT - Image Guided Radiation therapy) and related topics such as small- field dosimetry. The training is carried out through the UCLA Biomedical Physics Interdepartmental Graduate Program. This program has been training pre- and postdoctoral trainees for more than 50 years (35 of which with NIH training grants), in ways that bring together researchers from these basic fields with investigators in the clinical translational sciences and physicians who are truly clinical researchers, all in a common environment dedicated to bringing basic research to clinical applications. This marriage of physical sciences, biology, mathematics and medicine has produced successful biomedical research and aims to continue to do so in the future. The UCLA Biomedical Physics Interdepartmental Graduate Program has had an exemplary record in training individuals for these roles at the predoctoral and postdoctoral level. It has the programmatic infrastructure in place for the program, it continues to innovate both in research and in teaching and most important, it has a dedicated and outstanding faculty.